UNTEMPERED STEEL FOR HOT CASTING HOT CASTED UNTEMPERED ARTICLE AND METHOD FOR PRODUCING SAME

摘要

The present invention has as its object the provision of a non-quenched and tempered steel for hot 5 forging use which enables induction hardening and a hot forged non-quenched and tempered part and method of production of the same which control the structure inside a part by cooling after hot forging so as to suppress the drop in cuttability accompanying high strength and to 10 improve the fatigue strength. The present invention steel is characterized by comprising, by mass%, C: 0.45 to 0.60%, Si: 0.02 to 0.15%, Mn: 1.50 to 3.00%, P: 0.0002 to 0.150%, S: 0.001 to 0.200%, Cr: 0.02 to 1.00%, Al: 0.001 to 0.300%, V: 0.01 to 0.30%, Mo: 0.03 to 1.00%, and N: 15 0.0020 to 0.0070% and having a balance of Fe and ) unavoidable impurities. An induction hardenable hot forged non-quenched and tempered part which is comprised of the same steel composition, has a steel structure of an area ratio 95% or more bainite structure, and has Mo 20 carbonitrides dispersed in the steel and a method of production of the same.